Transcription in various regions of the mammalian (mouse brain) will be examined using nuclear RNA and specific single copy probe DNA. These experiments will be designed to test whether or not transcriptional differences between different anatomical regions of the brain can be detected. Messenger RNA populations in different anatomical regions of the brain will be examined. The complexity of poly(a) minus and poly(a) plus mRNA species will also be reevaluated. Preliminary evidence suggests a complex class of poly (a) minus mRNA may exist. Further experiments will be done to verify this initial finding. Finally, the relationship of large nuclear hnRNA molecules to the production of messenger RNA will be examined. Procedures have now been developed which permit isolation of hnRNA molecules on the basis of molecular weight since aggregation has been eliminated. Both steady state and pulse labeled hnRNA molecules will be used in these experiments. cDNA will be used to identify messenger sequences in hnRNA.